As you know, the following code publishes the latest content in a group in its WordPress

<?php
            $my_query = new WP_Query('showposts=1&cat=172');
            while ($my_query->have_posts()):
            $my_query->the_post();
            $do_not_duplicate = $post->ID;
            ?>

I want to make changes to this code so the last article in a group is not displayed and the pre-final content of the same group will be displayed. thank u